Which one of the following statements is correct?

• A
  Manganese salts give violet borax bead test in the reducing flame
• B
  From a mixed precipitate of $AgCl$ and $AgI$,ammonia solution dissolves only $AgCl$
• C
  Ferric ions give a deep green precipitate on adding potassium ferrocyanide solution
• D
  On boiling a solution having $K^{+}$,$Ca^{2+}$ and $HCO_3^-$ ions we get a precipitate of $K_2Ca(CO_3)_2$